48 lines
2 KiB
TeX
48 lines
2 KiB
TeX
\NeedsTeXFormat{LaTeX2e}
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\ProvidesPackage{mkessler-findpackage}[2021-09-06 - Find a package that provides some command]
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%%%%
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% This is just a quick packaging of the post by
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% 'Martin Nyolt' (https://tex.stackexchange.com/users/78783/martin-nyolt)
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% found at
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% https://tex.stackexchange.com/users/78783/martin-nyolt
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% Note that SO answers are by default CC BY-SA 3.0 licensed, see
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% https://creativecommons.org/licenses/by-sa/3.0/
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\def\find@load#1[#2]#3[#4]{%
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% load the package
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\find@fileswith@pti@ns{#1}[#2]{#3}[#4]%
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% check if commands exists now
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\ifcsname\find@command\endcsname
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\typeout{Package #3 introduces command \find@command.}%
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% command has been found, revert to original version without checks
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\let\@fileswith@pti@ns\find@fileswith@pti@ns
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\else
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% somehow, \@fileswith@pti@ns is restored after loading a package
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% thus, patch it again
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\let\@fileswith@pti@ns\find@load
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\fi
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}%
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\newcommand*{\findpackagebycommand}[1]{%
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% using this multiple times - esp. when the package has not been found yet -
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% will break things. Thus, check first that \find@command has never been defined before
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\ifx\find@command\undefined
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\def\find@command{#1}%
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% first, check if this command is already defined
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\ifcsname\find@command\endcsname
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% in this case, just issue a warning and do nothing
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\@latex@warning@no@line{Command \find@command \space is already defined}%
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\else
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% overwrite the internal \@fileswith@pti@ns command, which does the actual loading
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% \@fileswith@pti@ns is used internally by \usepackage and \RequirePackage
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\let\find@fileswith@pti@ns\@fileswith@pti@ns
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\let\@fileswith@pti@ns\find@load
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\fi
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\else
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% used multiple times - prevent and give a warning
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\@latex@warning@no@line{You can use \protect\findpackagebycommand \space only once}%
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\errmessage{Invalid use of command findpackagebycommand.}%
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\fi
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}
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